The present invention relates to a diaphragm fluid pump, and more particularly to an improvement of a diaphragm fluid pump driven by swinging movement of a rocker arm.
In related U.S. Pat. application Ser. No. 533,216, now U.S. Pat. No. 3,969,045 file on Dec. 16, 1974, the inventors disclosed a diaphragm fluid pump of the type having a diaphragm piston assembly hermetically assembled within a pump housing and reciprocated by a pump drive shaft by way of a rocker arm, and a pumping chamber defined by the diaphragm piston within the pump housing, wherein a cushioning material made of such a soft resilient material as rubber, soft synthetic resin or the like is integrally secured on the inner surface of the diaphragm piston assembly within the pumping chamber. This cushioning material functions to reduce the pumping chamber volume to a possible minimum on the arrival of the diaphragm piston at its upper dead point and also to absorb shocks produced when the diaphragm piston touches the inner wall of the pump housing.
Even with a diaphragm fluid pump of the abovementioned type, there is such a problem that when the operating rod of the diaphragm piston assembly wavers in its reciprocation, the cushioning material loses some of its buffer effect by its swingable engagement with the inner wall of the pump housing on the arrival of the diaphragm piston at its upper dead point; also the flexible diaphragm is twisted to lessen its durability.